California, New Jersey and Illinois continue to have the highest concentrations of markets most at risk of housing downturns, according to new data from Attom.

In fact, per the analytics company’s study, which was derived from evaluating home affordability gaps, underwater mortgages, foreclosures and unemployment, nearly half of the counties most vulnerable to housing issues were in the three states. Some of the largest clusters of at-risk counties were around the sprawling metropolises of New York City and Chicago, as well as in inland California.

Counties were assessed based on the share of homes facing possible foreclosure; the percentage of homes with mortgage balances exceeding estimated property values; the percentage of average local wages required to pay for major homeownership costs on median-priced single-family homes; and local jobless rates. Counties were ranked in each category, with the overall conclusion then based on a combination of the four ranks.

Three counties in New York City proper — Kings County (Brooklyn), Richmond County (Staten Island) and Bronx County — along with four in the Big Apple’s suburbs (New Jersey’s Essex, Passaic, Sussex and Union counties) were among the 50 counties deemed most at risk. Also included were five Illinois counties in and around Chicago — Cook, Kendall, McHenry and Will — as well as neighboring Lake County in Indiana.

Several others are in inland California: Butte (Chico), Humboldt (Eureka), Solano (outside Sacramento) and Shasta (Redding) counties in northern California, and Kern (Bakersfield), Kings (outside Fresno), Madera (outside Fresno), Merced, San Joaquin (Stockton) and Stanislaus (Modesto) counties in the central part of the state.

Many of the counties in and near New York City landed on the list for a familiar reason: seriously unaffordable homeownership costs. In Kings County, for example, a whopping 111.8% of average local wages are needed for major homeownership expenses. For many of California’s inland areas, it was high unemployment that landed counties at risk. Of the counties most vulnerable to housing downturns, Merced County at 9.4% had the highest jobless rate.

“While these observations don’t indicate immediate red flags or warning signs of an impending downturn, they do highlight areas of relative risk,” said Rob Barber, Attom’s CEO. “With the housing market still facing challenges, it’s crucial to closely monitor regions where key indicators suggest a higher likelihood of issues.”